Software is being developed (with NIAMS and BEIP) to analyze viral and bacterial images and perform various statistical and mathematical tests. Such images are typically analyzed by Fourier filtering techniques, and the use of correlation alignment together with correlation averaging, and three-dimensional Fourier reconstruction techniques. The electron micrographs are taken with a Philips EM400T microscope, a Zeiss 902 microscope, and the Brookhaven STEM. Some micrographs are preselected by optical diffraction. Negatives are digitized on a Perkin- Elmer 1010MG microdensitometer and analyzed by means of the PIC computer system. Results are photowritten on the Perkin-Elmer microdensitometer and on a Matrix camera station. Image processing uses software developed primarily at NIH. We anticipate evaluating other viruses and bacteria for suitability for examination with these methods, and continuing with this ongoing project to determine the structure of various classes of viruses.